Modern mobile communication devices are used for a wide range of purposes in addition to traditional telephony. For example, it is known to use instant messaging or email to send messages that include multimedia objects such as images, audio files and video clips. Such messages often include large amounts of data that a user may wish a network to store independently of the messages they were originally attached to.
The Open Mobile Alliance (OMA) is developing a Converged IP Messaging (CPM) specification that provides for the convergence of multi-media communication services. The Open Mobile Alliance publishes much of its work on its website (www.openmobilealliance.org).
FIG. 1 shows a system, indicated generally by the reference numeral 2, comprising a client device 4 and a central system 6. The client device 4 includes a message and media storage client 8. The central system 6 includes a message and media storage server 10. The client device 4 may be a CPM-enabled device and the central system 6 may be a CPM system.
The message and media storage server 10 provides management and storage functions for messages and other media and is used, for example, to store users' multimedia data. The message and media storage client 8 manages a particular user's resources at the server 10 and also manages the resources stored locally at the client device 4.
The message and media storage server 10 may be one component or consist of two components, one storing messages and another one storing media. The same can hold for the client side, i.e., it can host a message storage client and a media storage client.
Data stored in the message and media storage server 10 can be classified in two different ways:                1. Message-like contents (such as CPM messages, CPM conversations, and CPM session histories, including their attachments); and        2. Unstructured contents, e.g. plain binary files (of any type).        
In some circumstances, a user may wish to transfer an attachment of a message from an area storing message-like contents (including the said attachment) to an area containing plain binary files. This may, for example, be done when a user is no longer interested in the whole message, but would like to keep the attachment. For example, if a user receives a message including an image as an attachment, the user may wish to copy the image to a separate location and then delete the original message.
FIG. 2 is a flow chart 20 showing, in broad terms, how such an attachment may be transferred. The flow chart 20 includes a first step 22 in which the attachment is downloaded from the message and media storage server 10 to the client 4. Next, at step 24, the attachment is uploaded from the client 4 to the area of the server 10 that stores plain binary files.
The transfer of data via the client device 4 involves two over-the-air data transmissions. In the event that the end file is not stored at the client device 4, these over-the-air transmissions represent an unnecessary use of network resources.
The present invention seeks to address at least some of the problems outlined above.